JP5678169B2 - Janus iron-silicon oxide particles - Google Patents

Description

  The present invention relates to spherical and / or spheroidal iron-silicon oxide particles, said particles having two parts, wherein one part consists essentially of silicon dioxide and the other The part consists essentially of iron oxide. Moreover, the present invention relates to a method for producing the particles and the use of the particles.

  Adv. Mater. 21 (2009), 184-187 discloses a simplified method of so-called Janus particles from silicon dioxide and maghemite. These Janus particles are spherical particles having an average particle size of 71 ± 33 nm, with one hemisphere consisting of amorphous silicon dioxide and the other hemisphere consisting mainly of maghemite. Janus particles can be obtained by flame burning a solution of methanol, approximately equimolar amounts of acetylacetone iron (III) and tetraethoxysilane. What is important here is that, in contrast to the usual spray pyrolysis method, it is not atomized by the gas and the flame load is clearly reduced. The publication does not disclose that the magnetic properties of these Janus particles can vary. The disadvantage of this method is the fact that the amount obtained is linked to laboratory scale and that diversion to the process on an industrial scale cannot be derived from the disclosure.

  On the other hand, a method for producing a silicon-iron mixed oxide is known in the prior art, however, the method does not exist in the form of Janus particles. For example, EP-A-1284485 discloses silicon-iron mixed oxide particles, wherein the domains of the mixed oxide component are present in or on the matrix of the quantitatively higher mixed oxide component. ing. WO 2008/148588 discloses a silicon-iron mixture powder in the form of spatially separated agglomerates of silicon dioxide and iron oxide having an average particle size of iron oxide of 2 to 100 nm. The aggregate has a three-dimensional structure as shown in FIG. 1 of WO2008 / 148588. Further, FIG. 1 schematically shows the dispersion of the mixed oxide component in the primary particles. Further disclosed is that silicon dioxide as a mixed oxide component can form a shell around iron oxide, and the iron oxide phase maghemite and magnetite can dominate. The silicon-iron mixed oxide powder is produced by flame spray pyrolysis of a vaporous chlorosilicon compound and an aqueous iron chloride solution.

  The technical problem of the present invention was therefore to provide particles that have the special chemical and physical properties of Janus particles and whose magnetic properties can be tailored to each application. A further object of the present invention was to provide a process for the production of these particles which makes it possible to obtain quantities on a technical scale.

The subject of the present invention is a spherical and / or spheroidal iron-silicon oxide particle, said particle having two parts, one part consisting essentially of silicon dioxide. And the other part consists essentially of iron oxide,
a) the proportion of iron oxide calculated as silicon dioxide or Fe ₂ O ₃ is 10 to 90% by weight, and b) the proportion of iron oxide is
Maghemite 5-75% by mass,
Magnetite 20-90% by mass,
Hematite 0-15% by mass,
β-Fe ₂ O ₃ 0-5% by mass
Is included.

  The iron-silicon oxide particles according to the invention are preferably predominantly spherical, and / or spheroidal, i.e. more than 50%, usually more than 80%, in each case based on the total amount of particles. In that case, the particles have two parts, one consisting essentially of amorphous silicon dioxide and the other consisting essentially of iron oxide. The ratio can be determined by methods known to those skilled in the art, for example by counting from TEM photographs. The structure of the iron-silicon oxide particles can be ascertained by electron micrograph (TEM). FIG. 1 shows a particle according to the invention. A concave interface passes through approximately the middle of the particle, which separates the iron oxide side labeled A (dark part) from the silicon dioxide side labeled B (bright part). ing. The particles according to the invention are advantageously present as independent individual particles.

The iron-silicon oxide particles according to the invention show reflections that can be assigned to maghemite, magnetite, hematite and β-Fe ₂ O ₃ in the X-ray diffraction diagram. The silicon dioxide content of the particles according to the invention is X-ray amorphous. Furthermore, an X-ray amorphous iron oxide component having a ratio of up to 10% by mass based on the total amount of iron oxide may be present. The ratio of these X-ray amorphous iron oxides can be estimated from an X-ray diffraction diagram.

  It may be advantageous to have iron-silicon oxide particles with a proportion of maghemite and magnetite higher than 80% by weight, particularly preferably higher than 90% by weight, in each case based on the iron oxide proportion. Such particles exhibit a high maximum reached temperature upon excitation in an alternating or alternating electromagnetic field.

  Furthermore, iron-silicon oxide particles in which the proportion of iron oxide is 40 to 90% by mass and the proportion of silicon dioxide is 10 to 60% by mass may be advantageous. In such embodiments, the particles are generally or predominantly present in a form exhibiting iron oxide and silicon dioxide hemispheres. This composition can be determined by methods known to those skilled in the art, such as X-ray fluorescence analysis (RFA).

  The sum of the proportions of iron oxide and silicon dioxide in the particles according to the invention is usually at least 98% by weight, preferably at least 99% by weight. Furthermore, the particles according to the invention may contain 0.01 to 0.1% by weight of carbon.

Furthermore, the BET surface area of the iron-silicon oxide particles according to the invention is preferably 1 to 100 m ² / g, particularly preferably 10 to 70 m ² / g, very particularly preferably 15 to 35 m ² / g.

A further subject of the invention is a process for the production of iron-silicon oxide particles, in which a reactor comprising reaction zones I, reaction zone II, cooling zone and separation zone, which are continuous zones,
a) Within reaction zone I, optionally together with a carrier gas, contains one or more hydrolyzable and / or oxidizable silicon compounds and one or more oxidizable and / or hydrolyzable iron compounds An aerosol of 10 to 90% by weight, preferably 40 to 90% by weight of iron compound calculated as Fe ₂ O ₃ and 90 to 10% by weight of silicon compound calculated as SiO ₂ , preferably Are combined in a ratio containing 10 to 60% by mass based on the total of iron compound and silicon compound,
b) the mixture is evaporated by an indirect flame, wherein the indirect flame is obtained by ignition of a mixture comprising air or oxygen-enriched air and one or more hydrogen-containing combustion gases; And the amount of oxygen is at least sufficient to ensure complete reaction of the hydrogen-containing combustion gas and the hydrolyzable and / or oxidizable silicon and iron compounds, the conditions for the apparatus being this vapor, in the form of a laminar flow, preferably less than 4 ms ^-1, selected particularly preferably away the reaction zone I at an average rate of 1～4Ms ^-1 and c) this mixture reaction zone, II, in reaction zone II, it reacts with the oxygen still present and the reaction products formed during the generation of indirect flames, with laminar flow conditions in reaction zone II (Stroemungsverhaeltnisse) Advantageously, the average velocity of the stream is less than the average velocity in reaction zone I, and the average residence time of the reaction mixture in reaction zone II is at least 1 second, advantageously 1 to 10 seconds, particularly preferably 3 to 7 seconds,
d) Subsequently, in the cooling zone, the reaction mixture is cooled to a temperature of 200-400 ° C. by supplying water, and e) in the separation zone, solids are separated from gaseous or vaporous substances. To do.

FIG. 3 schematically shows an embodiment of the method according to the invention. that time,
A is one or more iron compounds;
B is one or more silicon compounds;
C is a gas containing oxygen, such as air, and / or an inert gas, such as nitrogen;
D is a hydrogen-containing combustion gas, preferably hydrogen;
E is water;
F is the result of C + D and within reaction zone I a flame without direct contact with the mixture from A and B (indirect flame);
I is reaction zone I;
II is reaction zone II,
III represents the cooling zone and IV represents the separation zone.

The process according to the invention can advantageously be carried out with an excess of air. This excess is suitably written as lambda, where lambda contains oxygen divided by the oxygen requirement essential for complete oxidation of hydrogen-containing combustion gases, iron and silicon compounds. The quotient from the oxygen content of the gas is defined in mol / h each time. Accordingly, lambda = 1 corresponds to the amount of oxygen that is just sufficient to completely react the hydrogen-containing combustion gas and the iron and silicon compounds depending on the stoichiometry. Advantageously, in the present case, a lambda of 1.2 to 2 is advantageous. A prerequisite for the process according to the invention is that the silicon and iron compounds are hydrolysable and / or oxidizable. Suitable silicon compounds are silicon halide compounds such as SiCl ₄ , CH ₃ SiCl ₃ , (CH ₃ ) ₂ SiCl ₂ , (CH ₃ ) ₃ SiCl, (CH ₃ ) ₄ Si, HSiCl ₃ , (CH ₃ ) _{2. HSiCl, CH 3 C 2 H 5} SiCl 2, the general formula _{R n Cl 3-n SiSiR m} Cl 3-m [ wherein, R = CH ₃ and n + m = 2, 3, 4, 5 and 6] disilanes having, Or it may be an alkylsilane, such as Si (OCH ₃ ) ₄ or Si (OCH ₂ CH ₃ ) ₄ . Mixtures of these compounds can also be used. Advantageously, SiCl ₄ and / or Si (OCH ₂ CH ₃ ) ₄ are used. The iron compound may be an organic or inorganic iron compound such as iron chloride, iron nitrate, iron acetate, iron carboxylate or iron alkoxide. However, preferably iron (II) chloride is used.

The iron compound is used in the form of an aerosol in the process according to the invention. Aerosols are fine droplets. The average droplet diameter is preferably 0.1 to 100 μm. The aerosol can be obtained by atomization of a solution of an iron compound using an inert gas or a gas containing oxygen. The solution is preferably an aqueous solution having an iron compound content of 10 to 40% by weight calculated as Fe ₂ O ₃ .

  A further object of the invention is the welding of iron-silicon oxide particles in an alternating electromagnetic field as a component of an adhesive composition, as a component of a polymer preparation, as a component of a rubber mixture. As a component of the plastic composite obtained by the process of 1 and use for producing dispersions.

Diagram showing spheroidal particles each having a part from iron oxide and a part from silicon dioxide Diagram showing diffraction pattern of iron-silicon oxide particles according to the invention from Example 1 Fig. 1 schematically shows an embodiment of the method according to the invention

analysis:
X-ray diffraction diagram Measurement:
Reflection, θ / θ-diffractometer, Co-Kα, U = 40 kV, I = 35 mA;
Scintillation detector, downstream graphite monochromator Sample rotation Aperture: 2 x 8 mm, 1.0 mm, 0.4 mm
Angle range (2Θ) / step width / measurement time: 10 to 100 ° / 0.04 ° / 6 s (h)

Rating:
SOP: QLPA-CSM, QNPA-Rietbelt (CNPA-Rietveld), CRYST-Rietbelt (CRYST-Rietveld)
Qualitative phase analysis is performed based on PDF set 58 of ICDD database PDF 2.
Quantitative phase analysis and the crystallite size measurement, Rietveld program SiroQuant ^(R), performed using Version 3.0 of the (2005).

  FIG. 2 shows the diffractogram of the iron-silicon oxide particles according to the invention from Example 1.

  Hematite can be uniquely identified because of independent reflection. The reflections of magnetite and maghemite overlap for the most part. Maghemite is clearly detectable in the vorderer Winkelbereich based on the reflections (110) and (211).

  Quantitative phase analysis was performed by the Rietveld method (relative error of about 10%). This works well when maghemite is present, when all maghemite, magnetite and hematite of the phase are drawn. The general quality of Rietveld analysis in this system is an R value of up to about 0.3.

In addition, some samples contain β-Fe ₂ O ₃ .
The procedure is as follows:
− Background correction.
-Refinement of pure hematite with virtually no overlap.
-Optimal adjustment of maghemite non-overlapping reflection (acute angle range) and half width of reflection at position (Θ).
- Fe ₃ adjustment and refinement of maghemite as O ₄ (without element substitution).
-Estimate β-Fe ₂ O ₃ indirectly by evaluating the overlap with the strongest hematite reflection.
-Estimate the proportion of amorphous iron oxide.
-Crystallite size measurements are made within the Rietveld program after the end of quantitative phase analysis (ie including adjustment of the reflection profile). A half width of 0.12 ° was set as an apparatus parameter.

Example 1 (according to the invention): an aerosol with an average droplet size of <90 μm and vaporous tetrachloride obtained by atomization of 2 kg / h of a 25% iron (II) chloride solution in water and ³ Nm ³ / h of air a mixture of silicon 0.15 kg / h and air 2 Nm ³ / h, the reactor of the reaction zone were combined in I, and hydrogen 8 Nm ³ / h and indirect flame formed from an air Nm ³ / h Heat by. The maximum temperature at which the mixture leaves reaction zone I is 1032 ° C., and the average velocity of the laminar flow is 2.4 ms ⁻¹ with an average residence time of 0.4 seconds. This mixture is contacted in reaction zone II with a mixture resulting from the reaction of air and hydrogen. The maximum temperature in reaction zone II is 1057 ° C., and the average laminar velocity is 0.4 ms ⁻¹ with an average residence time of 5 seconds.

  This mixture is cooled in the cooling zone to a temperature of 241 ° C. by introduction of 1.2 kg / h of water. Subsequently, the solid content is separated by a filter.

The solid has an iron oxide ratio of 85% by mass calculated as Fe ₂ O ₃ and a silicon dioxide ratio of 15% by mass.

The resulting powder has a BET surface area of 13 m ² / g. TEM-EDX analysis shows spheroidal particles with parts from iron oxide and silicon dioxide, respectively (FIG. 1). From the X-ray diffraction pattern, the composition of the iron oxide phase of 12% by mass of maghemite, 85% by mass of magnetite, and 3% by mass of hematite is determined (normalization of hematite, magnetite, maghemite to 100%). The amorphous ratio of iron oxide is estimated to be 10% by mass. The silicon dioxide content is X-ray amorphous.

  Example 2 (according to the invention) is carried out in the same way. The raw materials and reaction conditions, and the physicochemical data of the resulting product are shown in Table 1.

  Example 3 (comparative example) is carried out in the same way as described from EP-A-1284485. The raw materials and reaction conditions, and the physicochemical data of the resulting product are shown in Table 1.

  TEM pictures of the powders from Examples 1 and 2 demonstrate a “Janus” -like structure. The powder from Example 3 does not have this structure. Rather, this TEM picture shows the presence of primary particles with iron oxide domains in and on the silicon dioxide matrix.

  The powders according to the invention of Examples 1 and 2 have a maximum reached temperature of 181 ° C. or 213 ° C. in an alternating magnetic field. For measurement, 200 mg of powder is pressed at a pressure of 1.5 tons. The resulting tablet had a smooth surface and sufficient stability. They are placed on an inductor on a slide and the temperature is measured contactlessly. The maximum attainable temperature is measured at 40 kHz (P = 1.9 kW, PWM = 750%; U = 560 V; t = 75 s; I = 3.4 A) using an MF instrument (medium frequecny instrument). . The maximum temperature noted is the average of the maximum temperatures from measurements of at least two tablets made from each sample.

１）水中で２５質量％の溶液を基準として；
２）例３：＋５Ｎｍ³／ｈを除き、微粒化空気＋３Ｎｍ³／ｈ
３）例３：１０＋３Ｎｍ³／ｈを除き、空気＋２Ｎｍ³／ｈ
４）平均流速；ＲＺ１＝反応ゾーンＩ；ＲＺ２＝反応ゾーンＩＩ；
５）平均滞留時間；ＲＺ１＝反応ゾーンＩ；ＲＺＩＩ＝反応ゾーンＩＩ
６）ＤＩＮ６６１３１に従ったＢＥＴ表面積

1) based on a 25% by weight solution in water;
2) Example 3: + 5 Nm except ³ / h, atomizing air + 3 Nm ³ / h
3) Example 3: 10 + 3 Nm except ³ / h, air + 2 Nm ³ / h
4) Average flow rate; RZ1 = reaction zone I; RZ2 = reaction zone II;
5) Average residence time; RZ1 = reaction zone I; RZII = reaction zone II
6) BET surface area according to DIN 66131

  A iron oxide side, B silicon dioxide side, A + C one or more iron compounds + oxygen containing gas and / or inert gas, B + C one or more silicon compounds + oxygen containing gas and / or inert gas, C + D Oxygen-containing gas and / or inert gas + hydrogen-containing combustion gas, E water, F indirect flame, I reaction zone, II reaction zone, III cooling zone, IV separation zone

Claims (15)

Spherical and / or spheroidal iron-silicon oxide particles, the particles having two parts, one part consisting essentially of amorphous silicon dioxide and the other the part Ri of substantially iron oxide formed, and the particles, the iron is present as a separate individual particles - in the silicon oxide particles,
a) the proportion of iron oxide calculated as silicon dioxide or Fe ₂ O ₃ is 10 to 90% by weight,
b) The iron oxide ratio is
Maghemite 5-75% by mass,
Magnetite 20-90% by mass,
Hematite 0-15% by mass,
β-Fe ₂ O ₃ 0-5% by mass
The iron-silicon oxide particles, characterized in that   2. The iron-silicon oxide particles according to claim 1, wherein the ratio of maghemite and magnetite is higher than 80 mass% in total based on the ratio of iron oxide.   The iron-silicon oxide particles according to claim 1 or 2, wherein the ratio of iron oxide is 40 to 90 mass% and the ratio of silicon dioxide is 10 to 60 mass%. The iron-silicon oxide particles according to claim 1, wherein the BET surface area is 1 to 100 m ² / g. A process for producing iron-silicon oxide particles according to any one of claims 1 to 4, in a reactor comprising reaction zones I, reaction zones II, cooling zones and separation zones which are continuous zones,
a) Within reaction zone I, a mixture comprising one or more hydrolyzable and / or oxidizable silicon compounds and one or more oxidizable and / or hydrolyzable iron compounds, Combine 10 to 90% by mass of iron compound calculated as Fe ₂ O ₃ and 90 to 10% by mass of silicon compound calculated as SiO _{2 at} a ratio containing the total amount of iron compound and silicon compound, respectively. And
b) the mixture is evaporated by an indirect flame, wherein the indirect flame is obtained by ignition of a mixture comprising air or oxygen-enriched air and one or more hydrogen-containing combustion gases; And the amount of oxygen is at least sufficient to ensure complete reaction of the hydrogen-containing combustion gas and the hydrolyzable and / or oxidizable silicon and iron compounds, the conditions for the apparatus being , vapor generated by indirect flame of the mixture leaves the reaction zone I in the form of a laminar flow, or one <br/> c) reaches the reaction zone II, the steam in the reaction zone II, Yi oxygen present as natural, and then selected to react with the reaction products formed during the generation of indirect fire, in which the laminar flow exists even in the reaction zone II, this time, the reaction zone II Within the reaction mixture The average residence time is at least 1 second,
d) Subsequently, in the cooling zone, the reaction mixture is cooled to a temperature of 200-400 ° C. by supplying water, and e) in the separation zone, solids are separated from gaseous or vaporous substances. A method for producing the iron-silicon oxide particles, wherein: 6. A method according to claim 5, characterized in that the laminar flow in which the vapor leaves the reaction zone I has an average velocity of 1-4 ms- ¹ .   The process according to claim 5 or 6, characterized in that the laminar flow in the reaction zone II has an average velocity which is smaller than the average velocity in the reaction zone I. 8. A process according to any one of claims 5 to 7, characterized in that the average residence time of the reaction mixture in the reaction zone II is 1 to 10 seconds. The quotient obtained by dividing the oxygen content of the gas containing oxygen in mol / h by the oxygen requirement essential for complete oxidation of the hydrogen-containing combustion gas, iron compound and silicon compound is 1.2-2. 9. A method according to any one of claims 5 to 8, characterized in that   10. A process according to any one of claims 5 to 9, characterized in that the silicon compound is brought into the reaction zone I together with a carrier gas.   The method according to claim 5, wherein the silicon compound is a halogenated silicon compound.   12. A process according to any one of claims 5 to 11, characterized in that the iron compound is iron (II) chloride.   13. A process according to any one of claims 5 to 12, characterized in that the aerosol is obtained by atomization of a solution of an iron compound using an inert gas or a gas containing oxygen. It said solution, characterized in that an aqueous solution having a Fe ₂ O ₃ calculated 10 to 40% by mass of iron compounds content as method of claim 13, wherein.   As a component of a rubber mixture, as a component of a polymer preparation, as a component of an adhesive composition, as a component of a plastic composite obtained by welding in an alternating electromagnetic field, and as a dispersion Use of the iron-silicon oxide particles according to any one of claims 1 to 4 for the production.

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